Studying the Effectiveness of an Expired Betamethasone Drug in Sulfuric Acid Solutions to Examine the Corrosive Behavior of Copper Using Weight Loss and Experimental Design

Abstract

Utilizing expired pharmaceuticals as corrosion inhibitors for copper in acidic environments offers compelling advantages, including cost-effectiveness, reduced toxicity compared to traditional inhibitors, and contribution to pharmaceutical waste reduction through recycling. This study investigates the corrosion inhibition of copper in a sulfuric acid solution using varying concentrations of Expired Betamethasone Drug, employing weight loss and Experimental Design methods. The influence of temperature on copper's corrosion behavior is examined within the range of 293–333 K. Results show that inhibition efficiency increases with higher inhibitor concentrations but decreases with rising temperature. Thermodynamic analyses elucidate adsorption and activation processes, revealing that the adsorption of Expired Betamethasone Drug on copper surfaces is characterized as endothermic and spontaneous, aligning well with the Langmuir and Frumkin adsorption isotherms. The activation and free energies of inhibition reactions support a mechanism of physical adsorption. To establish the relationship between factors and responses, we employ response surface methodology (RSM) with regression statistical analysis and probabilistic assessment. Statistical analysis demonstrates highly significant quadratic models for inhibition efficiencies (IE) with a coefficient of multiple regressions (R²) of 0.999. Further model validation confirms a strong fit (adjusted R² = 0.997), with experimental observations closely matching predictions and a highly significant model (Q² = 0.989). The findings reveal that this expired drug exhibits substantial inhibitory power, exceeding 96%, in both experimental and predictive calculations.